1. Field of the Invention
This invention relates to a new type of bone fastener that is suited for implantation either in a fractured shinbone (tibia) or a fractured thighbone (femur).
2. Description of Related Art
FIGS. 7 and 8 are schematic diagrams showing the implantation of a conventional shinbone fastener 1 in a shinbone 4. As shown, the shinbone fastener 1 is an elongated steel tube having a bent tail portion 10, a middle portion 11, and a frontal portion 12. The bent tail portion 10 is formed with a pair of screw holes 131, 132, and the frontal portion 12 is also formed with a pair of screw holes 133, 134. The longitudinal axis 101 of the bent tail portion 10 is angled with respect to the longitudinal axis 111 of the middle portion 11 by a predetermined angle. This angled design is required to allow the shinbone fastener 1 to be easily inserted from the top end 41 of the shinbone 4 to the inside of the shinbone 4.
As shown in FIG. 8, when the shinbone fastener 1 is implanted in position in the shinbone 4 (i.e., when the frontal portion 12 reaches the bottom end of the shinbone 4), bolts 14, 15, 16, 17 are screwed into the screw holes 131, 132, 133, 134 respectively so as to secure the shinbone fastener 1 firmly in position in the shinbone 4.
When the bolts 14, 15, 16, 17 are screwed in position, they are substantially parallel to each other since all the screw holes 131, 132, 133, 134 are oriented substantially in perpendicular to the longitudinal axis of the shinbone 4. One drawback to this design, however, is that when the user moves on foot at fast paces, it can cause the bolts 14, 15, 16, 17 to be easily loosened off position and thus cause injury to the shinbone 4.
FIGS. 9 and 10 are schematic diagrams showing the implantation of a conventional thighbone fastener 2 in a thighbone 5. As shown, the thighbone fastener 2 is also an elongated steel tube having a bent tail portion 20 formed with a pair of screw holes 21, 22 which are oriented in an angled manner with respect to the longitudinal axis of the thighbone 5. As illustrated in FIG. 9, when the neck part 50 of the thighbone 5 suffers from fracture, a pair of elongated bolts 24, 25 can be screwed respectively into the screw holes 21, 22 so as to fastened the fractured neck part firmly together. Furthermore, a third screw hole 26 is formed near the top end of the thighbone fastener 2. As illustrated in FIG. 10, when the main part of the thighbone 5 suffers from fracture, an elongated bolt 27 can be screwed into the screw hole 26 so as to fastened the fractured part firmly together.
One drawback to the forgoing bone fasteners, however, is that they are suited only to one kind of bone, i.e., either to the shinbone or to the thighbone, but not both, which makes the use of them quite cost-ineffective. There exists therefore a need for a new type of bone fastener that is suitable for use in shinbone and thighbone.